Push-pull electron tube



May 1, 1945. N. L. KISER 2,374,634

PUSH-PULL ELECTRON TUBE Filed July 24, 1942 /VA 771/; lY/EL l K/kE/ INVENTOR BYXA ATTORNEY Patented May 1, 1945 PUSH-PULL ELECTRON TUBE Nathaniel L. Kiser, Emporium, Pa., assignor to Sylvania Electric Products Inc., a corporation of Massachusetts Application July 24, 1942, Serial No. 452,178

2 Claims.

This invention relates to electron tubes and more especially to electron tubes for use in ultra high-frequency circuits.

A principal object of the invention relates to an electron tube of the duplex or push-pull pentode type for use in ultra high-frequency circuits wherein all the electrodes are substantially symmetrically mounted with respect to the various lead-in wires.

Another object is to provide an ultra highfrequency push-pull or balanced amplifier tube in which the high frequency return currents from the two anodes to the common cathode cancel each other out not only in the common cathode lead but in substantially all sections of the cathode itself.

A further object is to provide a duplex pentode tube for push-pull or balanced operation wherein a single cathode is employed and in which each section of the pentode receives electron emission from the full length of the cathode.

A feature of the invention relates to a balanced doluble section or push-pull shield grid tube having a common cathode with two separate control grids and two separate anodes and a common shield grid; both sections using the full length of the common cathode.

Another feature relates to a push-pull pentode mount in which two separate control grids, each cooperating with the full length of a common cathode, have substantially the same grid-tocathode spacings.

A further feature of the invention relates to a double pentode mount of a simplified construction.

A still further feature relates to the novel organization, arrangement and relative location of parts which constitute an improved balanced double pentode tube for high frequency circuits.

Other features and advantages not specifically enumerated will be apparent after a consideration of the following detailed descriptions and the appended claims.

In the drawing:

Fig, 1 is a vertical elevational view partly sectional of a tube embodying the invention.

Figs. 2 and 3 are respectively cross-sectional views of Fig. 1 taken along the lines 2-2 and 3-3 thereof.

Fig. 4 is another view of the electrode arrangement with certain parts omitted for clarity.

Fig. 5 is a schematic view showing the manner of connecting the various electrodes to the tube prongs.

Referring to the drawing, there is shown a tube comprising a glass bulb I which is closed off at its lower end by a flattened glass header through which are sealed the various lead-in pins 2-9. For a detailed description of a bulb and header of this type, reference may be had to U. S. Patent No. 2,250,184.

Supported on the inwardly projecting ends of the pins is an electrode assembly which-is preferably of the so-called unitary mount type including lower and upper insulator spacer discs ill, I I, between which the electrodes are mounted.

These electrodes include a central flattened tubular indirectly heated cathode sleeve I2 which is internally heated by an insulated heater wire or filament (not shown) in the manner well understood in the art. Arranged in planar alignment with each other and with the cathode sleeve are side rods l320, the opposite ends of which project through corresponding aligned Openings in the respective mica discs H], II. Another set of four metal uprights 2 I-24 are provided, these latter uprights being arranged in pairs, with the plane of one pair parallel to that of the other and also parallel to the flattened faces of the cathode sleeve l2.

Fastened in any suitable manner to the uprights 2|, 22, is a planar metal plate electrode 25; and a similar metal plate electrode 26 is fastened to the uprights 23, 24. Thus, the said plate electrodes are held rigidly parallel to the corresponding flat faces of the cathode i2. The mica spacer ll rests on the upper edge of plates 25, 26, and is held in place by suitable lugs 21, welded to the respective uprights 2l--24.

The mount is provided with a pair of control grids 28, 29: a shield grid 30; and a suppressor grid 3|. The control grids instead of being complete helical windings as in the customary construction, are, in accordance with the invention, in the form of half-helical grids. Thus, grid 28 consists of a series of fine wire laterals which are welded to the side rods l5, l6; while the grid 29 consists of a series of fine wire laterals welded to the side rods l3, I4. If desired, each control grid may be formed by a helical winding around the side rods as in the usual grid winding operation, and the half-helical turns on one side of the grid may be removed in any suitable manner. Thus, it will be seen that each of the control grids is the same average distance from the cathode, and notwithstanding that each grid is laterally offset with respect to the axis of the cathode sleeve, each grid exerts the same degree of control on the electron stream thus enabling each grid to cooperate with the full length of the corresponding flat side of the cathode sleeve. By this arrangement, the electrical advantages of so-called coplanar grids are achieved without entailing the high assembly costs which are a necessary concomitant of the usual coplanar grid construction. By using a flattened tubular cathode in conjunction with the laterally offset half grids, the tube can be used in push-pull r balanced ultra high-frequency circuits with the assurance that the high frequency cathode return currents from the two plates or anodes 25, 28, cancel out. not only in the common cathode lead. but substantially throughout the entire length of the cathode itself.

The shield grid 30 is of customary construction comprising helically wound fine wire laterals fastened to side rods l1, l8; and likewise for the suppressor grid ll which is fastened to side rods I9. 10.

Since the cathode is a flattened tubular member, the electrons from the opposite flat sides thereof, travel in opposite directions, one stream going to plate 25 and the other to plate 26.

Since the side rods ll, it, are in alignment with the edges of the cathode sleeve, there is negligible interference or cross-modulation between the two electron streams. If desired, the lateral edges of the cathode sleeve facingthe side rods i3, i8, may have the emissive coating removed therefrom prior to assembly. Another important advantage of this construction is that it enables the various electrodes to be connected substantially symmetrically to the lead-in pins 2-8 which may be arranged in a circle around the central axis of the electrode assembly as shown schematically in Fig. 5, wherein the pins 2 and 3 are the heater current supply pins and are connected to the cathode heater (not shown). One oi. these pins, for example the conventional high frequency balancedor pushnegative pin 2, may also be connected directly to the suppressor grid side rod I9. The cathode pin 4 is connected to the lower end of the cathode sleeve. The side rod H of control grid 29 is connected to the prong 5 while the side rod II of control grid 28 is connected to prong 8. The side rod 3 of the screen grid is connected to prong 1 while the side rods 2| and 23 of the respective plates 25 and 26 are connected to prongs 8 and 9. Thus all the connections from all the electrodes can be made at the lower end of the electrode assembly and these connections can be substantially symmetrical thu facilitating balancing of the circuits when the tube is used in art.

It will be understood of course that while the tube shows a cathode in the form of a flattened tube, any other equivalent flat strip or similar cathode may be employed providing there is substantially negligible electron emission from the edges of the cathode in alignment with the grid side rods. Furthermore, while the half-helical laterally offset construction is shown for the control grid, it will be understood that it may be applied to shield grids, suppressor grids, space charge grids and the like.

Various changes and modifications may be made in the disclosed embodiment without departing from the spirit and scope of the invention.

What I claim is:

1. An electron tube comprising an electronemitting cathode, a pair of separate anodes on opposite sides of said cathode, a pair of grids one between said cathode and each of said anodes, each grid having a pair of side rods and with the side rods of both grids located in substantially the same plane, and grid laterals extending across the side rods of each grid with the laterals of one grid located between the cathode and one anode and the laterals for the other grid located between the cathode and the other anode, said'cathode being in the form of a flattened tubular sleeve and the side rods of each grid are unequally spaced from the edges of the cathode with a side rod of each grid located between an edge of the cathode and a side rod of the other rid.

2. An electron tube comprising an electronemitting cathode, a pair of separate anodes on opposite sides of said cathode,.a pair of grids one between said cathode and each of said anodes, each-gridhaving a pair of side rods and with the side rods of both grids located in substantially the same plane, and grid laterals extending across the side rods of each grid with the laterals of one grid located between the cathode and one anode and the laterals for the other grid located between the cathode and the other anode, the central longitudinal axis of each grid being oil?- set laterally with respect to the central axis of the cathode, but with both grids having the same average distance from the cathode.

NATHANIEL L. KISER. 

